Aromatic polycyanates which are thermosettable to polytriazines are known, for example, from U.S. Pat. Nos. 3,448,079; 3,553,244; 3,694,410; 3,740,348; 3,755,402; 4,094,852 and 4,097,455. Aromatic polycyanates containing one or more mesogenic moieties in the main chain of the molecule which are thermosettable to polytriazines are known from copending application Ser. No. 07/380,938 filed Jul. 17, 1989.
Although the aforementioned aromatic polycyanates containing one or more mesogenic moieties in the main chain of the molecule provide cured products having excellent physical properties, they are often very difficult to process due to their relatively high melting temperatures. Thus, for example, when the mesogenic moiety is a benzanilide group present in the main chain of the dicycanate of 4,4'-dihydroxybenzanilide, melt flow to a birefringent fluid is not observed until 184.degree. C. In the present invention, when the benzanilide group is attached as a side chain to the dicyanate, melt flow to a shear birefringent fluid is observed at 69.degree. C. Therefore, it would be desirable to have available aromatic polycyanates containing one or more mesogenic moieties attached as lateral substituent(s) to provide lower melting temperatures which would lead to easier processing.
The present invention provides a method for attachment of one or more mesogenic moieties to a polycyanate as lateral substituent(s). Incorporation of said mesogenic moieties can lead to a molecular level ordering of the polytriazine thermoset (cured) composition thereof much similar to that found in the thermoset (cured) aromatic polycyanates which have one or more mesogenic moieties in the main chain. However, due to their relatively lower melting temperatures, the polycyanates of the present invention in which the one or more mesogenic moieties are lateral substituents can provide improved processibility.